Shear strength of reinforced concrete deep beams containing recycled concrete aggregate and recycled asphalt pavement

Abstract

In this study, the behavior of deep beams containing natural coarse aggregates (NCA), recycled concrete aggregates (RCA), and recycled asphalt pavements (RAP) is studied. Ten deep concrete beams with two length-to-depth ratios of 1.6 (group G1.6) and 2.7 (group G2.7) were constructed. In each group, one specimen was built with NCA concrete, two specimens were built with 50% of RCA and RAP replacement without mix design modification, and two specimens were built with 100% of RCA and RAP replacement with modifying the mix design to obtain the target compressive strength. The load–deflection curves, shear capacity of deep beams, absorbed energy, failure mode, cracking patterns, and strain in reinforcement bars were studied. The results showed by replacing NCA with 50% of RCA and RAP, the shear capacity of deep beams is reduced by 9 and 11.7% in G1.6 group and 4.66 and 7.52% in G2.7 group, respectively. Using 100% replacement of NCA with RCA and RAP and using the modified mix design to achieve the target compressive strength, the shear capacity of deep beams was nearly equal. The absorbed energy in deep beams containing RAP was higher than other specimens. Also, RAP deep beams had the highest and, RCA deep beams had the least reserved strength, showing the ductility of RAP and brittleness of RCA compared with NCA deep beams. The cracking patterns analysis showed that the number of flexural and diagonal cracks is reduced in RCA and increased in RAP specimens. The width of flexural and diagonal cracks was higher in RCA and less in RAP specimens than NCA specimens.